Pathologic characteristics of pediatric intracranial pilocytic astrocytomas and their impact on outcome in 3 countries: a multi-institutional study.

Pilocytic astrocytoma (PA) is one of the most common glial neoplasms in the pediatric population, and its gross total resection can be curative. Treatment of partially resected or recurrent tumors is challenging, and the factors associated with increased recurrence risk are not well defined. Identification of favorable and unfavorable factors can lead to a better understanding and management of patients with PA. We studied the pathologic characteristics of 116 intracranial PAs from 4 institutions representing 3 distinct geographic regions to identify factors that may be associated with biological behavior. The study included 65 boys and 51 girls with a median age of 6 years. Median follow-up for all patients was 101 months, during which time 38 patients had recurrence. Progression-free and overall survivals were better in patients who underwent gross total resection. We were not able to identify any differences in pathologic and molecular markers among the 4 institutions from 3 different countries. However, progression-free survival varied significantly among institutions. Sox-2 was the most prevalent stem cell marker in PA, and many tumors showed synaptophysin positivity. BRAF immunostaining was not useful in determining BRAF duplication. BRAF duplication was more typical of posterior fossa tumors. There was a strong correlation between BRAF duplication and pERK immunostaining, suggesting that the RAF/MEK/ERK pathway is active in these tumors. This finding has significant implications given its role in oncogen-induced senescence and possible influence on treatment decisions of subtotally resected tumors.